Sound attenuating air discharge terminal device



April 21, 1970 SOUND ATTENUATING AIR DISCHARGE TERMINAL DEVICE 2 Sheets-Sheet 1 Filed June 14, 1968 HAao'Lo MAw'aY BY OJD? me.

ATTORNEYS J. J. DIECKMANN E'rAL 3,507,354

April 21, 1970 SOUND ATTENUATING AIR DISCHARGE TERMINAL DEVICE 2 Sheets-Sheet 2 Filed June 14, 1968 [NVENTORS J'oHN J'. D\EC\ MANN 'l- Hmmm MAW BY BY o-muiwwbm (gamma.

ATTORNEYS United States Patent O 3,507,354 SOUND ATTENUATING AIR DISCHARGE TERMINAL DEVICE John J. Dieckmann', Rockingham, Va., and Harold Mawby, Grass Lake, Mich., assgnors to Dunham-Bush, Inc., a corporation of Delaware Filed .lune 14, 1968, Ser. No. 737,087 Int. Cl. F24f I3/06; F01n 1/24 U.S. Cl. 181-42 10 Claims ABSTRACT OF THE DISCLOSURE A sound attenuating air discharge terminal device for air conditioning systems using high velocity air, wherein a tubular liner of sound absorbing material, such as fiber glass formed with a binder, is joined to a terminator nozzle and has its interior surface directly exposed to the air flowing to the nozzle.

The present invention relates to terminal devices for air conditioning systems and more particularly to such terminal devices having integral sound attenuating characteristics, especially for use with high velocity air transmission ducts. Systems using these devices are described in copending application Ser. No. 690,253, Heating and Cooling System, by John J. Dieckmann, one of the coinventors named in the present application.

BACKGROUND AND OBJECTS OF THE INVENTION Heretofore, air conditioning systems have been designed to provide heating and/or cooling of spaces to be conditioned by conveying high velocity conditioned air to such spaces through air transmission ducts. An example of such a system is disclosed in the above-identified copending application. Such systems, however, introduce considerable problems of noise attenuation to keep down the noise level inherently generated by movement of the high velocity air through the ducts and through which the conditioned high velocity air is discharged into the spaces to be conditioned.

A primary object of the present invention is to provide a terminal device for high velocity air transmission ducts of air conditioning systems, which terminal device is capable of creating high discharge velocity as, for example, 2000 feet per minute or more, without creating objectionable noise.

An additional object is to provide a terminal device for high velocity air transmission ducts of air conditioning systems, which (terminal device has the capability of attenuating noises created upstream of the device.

An additional object is to provide a terminal device of the type described having minimum resistance to air flow and having an essentially round discharge flow configuration.

An additional object is to provide an inconspicuous room terminal device for systems of the type described which is small in size and aesthetically acceptable.

A further object is to provide a device of the type described having means for shutting off the flow of air or adjusting the flow rate without creating objectionable noise.

Still further objectives are to provide a device of the type described which can be installed within a nominal 6nch joist space commonly used in residential and apartment construction, which can be economically manufactured from readily available materials, and which will meet the requirements of applicable National Fire Protection Association standards.

Other objects, advantages and capabilities of the present invention will become apparent from the following de- 3,507,354 Patented Apr. 21, 1970 ICC tailed description, taken in conjunction with the accompanying drawings, illustrating two embodiments of the invention.

GENERAL DESCRIPTION OF THE FIGURES DETAILED DESCRIPTION OF THE INVENTION In the field of acoustics, acceptable ambient noise (sound) levels in any particular environment is generally determined by comparison to selected Noise Criteria (NC) curves for frequency bands within the human audible range. Noise is measured by commonly available instrumentation as sound pressure level in decibels for discrete frequency bands designated octave bands where the high frequency limit is twice the low frequency limit. Preferred center point frequencies used in development of this invention were 63, 125, 250, 500, 1000, 2000, 4000 and 8000 c.p.s. as specified in American Standard S1.6-1960. For apartments, hotels, churches, theatres and, more particularly, sleeping areas of homes, the Noise Criteria 30 (NC-30) curve has been regarded by those versed in the acoustic art as an acceptable acoustic standard to establish ambient sound pressure levels. Accordingly, the NC- 30 has been selected as the acoustic objective of an acceptable air conditioning system not to be substantially exceeded. Incumbent on the attenuating terminal device of this invention is sufficient attenuation capability to meet NC-30 curve.

In FIGURE l, curve A depicts the performance of a typical unattenuated terminal device when connected directly to the high velocity air transmission duct. This configuration can be noted to greatly exceed the NC-30 curve in the 6th and 7th octave bands approaching NC-50 and also significantly exceeds NC-30 in the 5th and 8th octave bands. The performance of a typical attenuated device is depicted on curve B which does not exceed the NC-30 curve at any point and is significantly below said curve for both the high and low end frequency octave bands.

To meet all usage requirements, we have determined that it is desirable to build our terminal device in two configurations, one with inlet and outlet in a straight line and one in the form of a angle. Performance characteristics of both are essentially alike and design principles are the same. The difference in arrangement is solely for convenience of installation.

Referring to FIGURES 2, 3 and 4, illustrating the elbow type terminal device constructed in accordance with the present invention, the terminal device, indicated generally by the reference character 9, includes a tubular inlet bushing 10, for example of cylindrical configuration, for coupling the terminal device 9 to an upstream transmission duct, for example of the type illustrated in said earlier co-pending application Ser. No. 690,253, by slipping the transmission duct over the inlet bushing 10. A thin-'walled enclosing jacket or sleeve 12 encloses a tubular fiberglass liner 13 of annular cross-section, which matches the contour of the enclosing sleeve 12, and is permanently staked at one end to an annular gasket 16 which fits about a cylindrical inlet lbushing 10. The sleeve 12 is demountably attached at its other end, for example by means of screws threaded into tapped apertures in the sleeve 12, to terminator fitting 14 defining the air discharge opening in the floor, ceiling or wall of the room to be served by the conditioned air. The upstream end of the enclosing sleeve 12 may be sealed leak-tight to the enclosing jacket of the supply duct or transmission duct (not shown) by known means such as adhesive coated tape.

The inlet bushing 10 contains provision for pivotally mounting a valve blade 11 therein on a shaft 27 which extends transversely across the bushing 10. A control cable 17 has one end 17a thereof connected to the valve blade 11 and extends through a cable shield 19, inthe form of a small diameter tube, lwithin the enclosing sleeve 12 between the latter and the fiberglass liner 13, to a location near terminator fitting 14. The end of the cable shield 19 adjacent the terminator fitting 14 is secured to a lever mount 20, formed for example of a flat plate arranged in a plane paralleling a diametric plane of the exit orifice 14a of the terminator fitting and attached thereto, as by spot welding, along its lateral edges a. A valve-operating lever 18 is secured to one end of the control cable 17, and is pivotally mounted, as by rivet 18a, shown more clearly in the section view of FIG- URE 3, to the lever mount 20 for lfree rotation about the axis of the rivet 18a. The operating lever 18 is located so that the portion 18h of the lever 18 protrudes through the exposed face of the terminator fitting 14 alongside the exit orifice 14a, so that it can be actuated by the home owner by moving the lever 18 transversely from an open to a closed position as restricted by the slot 14b in the terminator fitting.

The terminator fitting 14 is attached to the wall, floor or ceiling 24 of the dwelling space designed to be served by the conditioned air. Its conguration, as best shown in FIGURES 2 and 3, is such that it defines an inner annular neck portion 14C defining the discharge opening 14a, a circular face plate portion 14d joined to and projecting outwardly from the exit end of the neck portion 14C, and an outwardly spaced cylindrical flange portion 14e projecting from the face plate portion 14d in outwardly spaced coaxial relation to the neck portion in the same direction as the neck portion 14C and for a suficient distance 'from the portion 14d to facilitate securement to the sleeve 12. The face plate portion 14d has a circular outer perimeter of a somewhat larger diameter than the flange portion 14e and has a short inwardly projecting cylindrical lip 14jl formed at the perimeter.

This terminator fitting 14 is designed to be inserted in a circular opening cut in a vertical wall, fioor or ceiling, hereinafter generally referred to as a boundary wall, of sufficient size to accommodate the neck andfiange portions 14c, 14e, and is conveniently installed in the opening 24a by a pair of diametrically oppositely positioned mounting screws 21 and spring toggles 22, as illustrated in FIGURE 3. The toggles 22 are of fiat spring material and comprise an inner leg 22a disposed parallel to the axis of the terminator fitting 14, a short outwardly projecting flange 22h at the end of leg 22a nearest the terminator fitting fiange 14e, having a threaded aperture therein into which the screw 21 is threaded, and an outwardly inclined leg 22e joined to the leg 22a at the other end thereof adapted to be compressed inwardly to fit through the hole 24a and having an inwardly curved free end portion to seat against the unexposed side of the boundary wall 24 to clasp the wall between the toggle 22 and the flange portion 14e of the terminator fitting 14, upon tightening of the screws 21. The toggles 22 are prevented from rotating by channel shaped clips 22 having an inner flange attached to the enclosing sleeve 12 and an outer flange which extends between the legs 22C and 22a of the toggles and bears against the latter. It will be noted that the terminator fitting 14 includes a throat section 26 of progressively reducing diameter from the edge of the neck portion 14C nearest tbe inlet bushing 10 TO approximately the axial center thereof, this being for the purpose of increasing the terminal velocity of the air, and includes a parting line 25 for plastic molding separation to minimize acoustical interference.

The tubular fiberglass liner 13 in a preferred embodiment employs fiberglass of about .00020 to .00025 inch diameter formed with a suitable low smoke generating binder, such as a phenolic binder, under heat and pressure to a density of about 3 pounds per cubic foot into an elbow shaped tube, for the terminal device of FIG- URES l to 4, or a straight tube, for the device of FIG- URE 5, to provide a tube having an internal diameter of about 11%6 inches and an external diameter of about 3 inches. The resultant liner material is equivalent to the material presently marketed by Johns Manville under thetradename, Micro-Lok. This liner 13 has an effective length of not less than one wave length of the lowest frequency of the unattenuated air stream that significantly exceeds acceptable sound pressure levels, for example, not less than about 41/2 inches.

The terminal device of FIGURE 5, indicated generally by the reference character 9 is constructed of the same basic components as the device 9 of FIGURES 2 to 4, designated 4by the same reference characters employed for the corresponding components of the embodiment of FIGURES 2 to 4, except that the fiber glass liner 13 and enclosing sleeve 12 are straight, rather than elbow shaped, to suit installation conditions where a straight terminal device `would be preferable.

The particular noise attenuating terminal device herein described provides a convenient and economical arrangement for appropriate discharge of high velocity conditioned air into the space to be conditioned, which iS extremely simple to install and which achieves improved sound attenuation by use of the sound-absorbing tubular fiber glass liner 13 having its interior surface exposed directly and uninterruptedly to the air stream over the whole distance between the inlet bushing 16 and the terminator fitting 14. By directly exposing the interior surface of the tubular liner 13 to the air stream without the presence of any perforated open mesh inner liner, helix, or other inner liner structure along the interior surface of the liner 13, sources of air turbulence or disturbance of air flow which would arise from the bounding edges of the perforations of perforated inner liners or from the spaced convolutions of helix liners are eliminated, thus avoiding the noise which would arise from such turbulence or air flow disturbance. The shut-off device provided by the valve blade 11 is also located and designed in such a way as to minimize generation of objectional noise and is disposed upstream of the noise absorbing liner 13 so that any noise generated by the shut-off device is attenuated by the liner 13.

While but two specific embodiments of the present invention have been particularly shown and described, it will be apparent that other modifications can be made within the spirit and scope of the invention.

What is claimed is:

1. A sound attenuating air discharge terminal device for air conditioning systems, wherein high velocity conditioned air is conveyed by a transmission duct to the space to be conditioned and discharged into the space through a boundary wall of the space predominantly along a discharge axis perpendicular to said bounding surface, comprising a terminal nozzle member of generally round configuration having a face plate portion to be mounted against the surface of the wall facing said space and inner and outer concentric annular flange portions projecting rearwardly from said face plate portion inwardly of the periphery thereof and defining a rearwardly opening annular channel therebetween, said nozzle having a central bore therethrough bounded by said inner flange portion and defining an exit orifice for discharge of the high pressure air into the space, inlet coupling means spaced upstream from the nozzle member relative to the direction of conditioned air flow to be coupled to the transmission duct, an elongated imperforate tubular sleeve secured at one end to said inlet coupling means and at its other end to said outer flange portion, and an integral tubular annular cross-section liner member of sound absorbing material enclosed within said sleeve and continuously spanning the space between said nozzle member and said inlet coupling means defining an air How conduit with its interior surface directly exposed to the air owing therethrough to maintain noise levels arising from conditioned air ow essentially below the Noise Criteria 30 curve.

2. A sound attenuating terminal device as defined in claim 1, wherein said sleeve is an integral molded tubular body of fiber glass formed with a binder under heat and pressure to a density of about 3 pounds per cubic foot.

3. A sound attenuating terminal device as defined in claim 1, wherein said liner has a length of not less than one wave length of the lowest frequency of the unattenuated air stream that significantly exceeds acceptable sound pressure levels.

4. A sound attenuating terminal device as defined in claim 2, wherein said liner has a length of at least four and one-half inches.

5. A sound attenuating terminal device as defined in claim 1, wherein said inlet coupling means is a substantially cylindrical tubular bushing, the interior surface of said annular liner at the upstream end thereof being disposed in coaxially surrounding engagement with a portion of said bushing, and said bushing having an annular gasket externally surrounding the same and secured thereto having substantially the same internal and external diameters as said liner, and means securely fastening said sleeve to said gasket in externally surrounding relation thereto.

6. A sound attenuating terminal device as defined in claim 3, wherein said inlet coupling means is a substantially cylindrical tubular bushing, the interior surface of said annular liner at the upstream end thereof being disposed in coaxially surrounding engagement with a portion of said bushing, and said bushing having an annular gasket externally surrounding the Same and secured thereto having substantially the same internal and external diameters as said liner, and means securely fastening s aid sleeve to said gasket in externally surrounding relation thereto.

7. A sound attenuating terminal device as defined in claim 1, wherein said inlet coupling means comprises a bushing including a valve blade of substantially elliptical peripheral configuration pivotally mounted therein on a transverse diametrically extending shaft for movement between closed and open positions within said bushing, a control cable connected to said valve blade eccentrically of said shaft and extending therefrom substantially along the interface between said liner and sleeve to said nozzle member, and lever means pivoted to said nozzle member having a portion connected to said cable and an actuator portion extending to an exposed position outwardly of said face plate portion for manual regulation of the angular position of the valve blade about said shaft be tween said open and closed positions.

8. A sound attenuating terminal device as defined in claim 6, wherein said inlet coupling means comprises a bushing including a valve blade of substantially elliptical peripheral configuration pivotally mounted therein on a transverse diametrically extending shaft for movement between closed and open positions within said bushing, a control cable connected to said valve blade eccentrically of said shaft and extending therefrom substantially along the interface between said liner and sleeve to said nozzle member, and lever means pivoted to said nozzle member havin-g a portion connected to said cable and an actuator portion extending to an exposed position outwardly of said face plate portion for manual regulation of the angular position of the valve blade about said shaft between said open and closed positions.

9. A sound attenuating terminal device as defined in claim 1, including resiliently deformable spring toggle members at circumferentially spaced positions outwardly adjacent said outer flange portion each comprising a first elongated leg extending along an axis paralleling the axis of said bore and an outwardly inclining leg projecting toward said face plate portion from an apex juncture with said first le-g to be flexibly deformed inwardly toward said axis upon introduction of said flange portions through an opening in said boundary wall and flexibly return outwardly following passage through said opening to engage free end portions of said inclined leg against rear surface portions of said wall and clamp the latter between said free end portion and said face plate portion, and screw means extending through said face plate portion and threadedly coupled to said first leg for adjustably positioning the toggle members axially of said bore.

10. A sound attenuating terminal device as defined in claim 8, including resiliently deformable spring toggle members at circumferentially spaced positions outwardly adjacent said outer flange portion each comprising a first elongated leg extending along an axis paralleling the axis of said bore and an outwardly inclining leg projecting toward said face plate portion from an apex juncture with said first leg to be flexibly deformed inwardly toward said axis upon introduction of said flange portions through an opening in said boundary wall and fiexibly return outwardly following passage through said opening to er1-gage free end portions of said inclined leg against rear surface portions of said wall and clamp the latter between said free end portion and said face plate portion, and screw means extending through said face plate portion and threadedly coupled to said first leg for adjustably positioning the toggle members axially of said bore.

References Cited UNITED STATES PATENTS 2,644,389 7/ 1953 Dauphinee. 2,858,760 ll/l958 Lathrop. 3,159,091 12/1964 Schutt 181--50 XR ROBERT S. WARD, I R., Primary Examiner U.S. Cl. X.R. 98--40 

